Laser diodes are widely used in high speed data communications. Modulated light from a laser diode may be used to carry information. The modulated light may be transmitted through optical fibers or across free space. For some data formats, when a laser diode emits light the data value is considered a logical one, and when the laser diode is off (e.g. where no light is emitted from the laser) the data value is considered a logical zero.
Vertical cavity surface emitting lasers (VCSELs) are one type of laser diode used in data communication networks. Drive circuitry may provide a VCSEL with sufficient current to turn on, thereby causing the VCSEL to emit light. Likewise, the drive circuitry may remove or prevent current from flowing to or through the VCSEL, thereby causing the VCSEL to turn off and not emit light.
The ability to drive a laser diode to generate a light intensity output has many applications. For example, generating a light intensity output enables the laser diode to encode information for transmission within an optical output signal. Generating a light intensity output also enables the laser diode to encode timed events (e.g. where a positive edge of a pulse denotes a start time) such as in time-of-flight detection where a received signal is used to determine and resolve distances between a target object and the laser diode. As signaling frequencies in high speed data communications increase (e.g. in excess of 1 GHz), it may be desirable to provide a method and a circuit for driving a laser diode to support robust optical communications even with such increases in signaling frequencies.